Observational study finds link between use of biotics and cognitive health

The research, published in 'Nutrients', concludes the data implies that nonfood pre- or probiotic use is a potential causal relationship and could be an effective strategy for improving cognitive function in elderly males.

There are multiple causes for cognitive impairment, but one potential factor is that the decrease of microbial diversity in elder individuals results in disruption of intestinal barrier permeability​.

Recent studies have revealed that gut microbiota can affect brain function and behaviour. The gut–brain axis not only maintains the muscular, sensory, and secretory pathways in the gastrointestinal tract but also affects brain growth, function, and behaviour​.

Compared with young people, elderly people have a lower abundance of beneficial microbiota, specifically Bifidobacterium​ and Lactobacillus​.

Animal studies have shown​ probiotic supplements can suppress the NF-κB signalling pathway mediated by TLR4 and RIG-I, as well as the inflammatory response, thereby improving cognitive function. Therefore, the intake of probiotics or prebiotics may have positive effects on human health.

The authors of the current study, from China, say that although some systematic reviews​ on the effects of pre- or probiotics on cognitive outcomes have been performed, no consistent conclusions have been drawn.

Therefore, the researchers aimed to better understand the role of nonfood pre- or probiotics in cognitive function in older adults through analysis of the National Health and Nutrition Examination Survey (NHANES) data (years 2011–2014).

The study

NHANES is a study adopting a multistage sampling approach to assess health conditions and lifestyle alterations in the United States. These data are collected through personal interviews, physical assessments, biological specimen collection, and field investigations involving representative samples from the national population.

The current study collected data on 19,931 individuals, then excluded interviewees under 60 years old (n = 16,299) and those with missing data on BMI, smoking, drinking, hypertension, stroke, diabetes mellitus (DM) and cardiovascular disease (CVD), and stroke (n = 745). Additionally, participants who lacked pre- or probiotic dietary supplement information (n = 923) and those who did not receive cognitive function tests or failed to complete cognitive tests (CERAD word learning test, Animal Fluency Test (AFT) and Digit Symbol Substitution Test) were also excluded (n = 176). Finally, 1788 participants were included.

The researchers analysed the Dietary Supplement Use 30-Day Study before the interview date to determine whether the sample used pre- or probiotics. 

The authors adopted some of the demographic data as covariates, including: age, gender, ethnicity, educational level, ratio of family income to poverty (PIR), body mass index (BMI), drinking, smoking status and disease history.

After analysing the data, the authors conclude that nonfood pre- or probiotic use was significantly positively correlated with comprehensive composite cognitive function among males participants, both before and after adjusting for demographic and confounding factors.

Moreover, obesity significantly altered the association between nonfood pre- or probiotic use and cognitive function suggesting that alterations in the gut microbiota may contribute to the prevention of cognitive impairment in older adults. 

Males and individuals with a BMI < 25 were more likely to benefit from nonfood pre- or probiotic use. Explaining this, the authors state: "It is well-known that elder women with higher oestrogen levels are at higher risk for Alzheimer’s disease. The observed gender dimorphism in cognitive function may be due to the metabolism of sex hormones regulated by the gut microbiota."

They add: "In the future, research focusing on the effects of specific probiotic and prebiotic types on individuals with different BMI levels may develop more personalized intervention strategies to meet the needs of different populations, thereby improving the success rate and applicability of these approaches. In addition, it is important to explore how obesity interferes with the effectiveness of prebiotics or probiotics."

However they note this study was observational, so causal inference is challenging. There may also be some unconsidered confounders which may bias results.

"Therefore, it just implies that nonfood pre- or probiotic use is a potential causal relationship and could be an effective strategy for improving cognitive function in elderly males," the report states.

They also note that the study only analysed whether the participants were using nonfood pro- or prebiotics, without quantifying any dietary intake. They also were unable to distinguish between long and short term use of the supplements.

They conclude: "Despite some limitations, the obtained results have been encouraging and motivating for further research in this direction. Further long-term prospective research is necessary."

Source: Nutrients

https://doi.org/10.3390/nu15153408​

"Association between Nonfood Pre- or Probiotic Use and Cognitive Function: Results from NHANES 2011–2014"

Chen, J.; Yang, N.; Peng, Y.; Zhou, H.; Li, Q.